Hewlett-packard Company

Turuvekere R Gururaja

Michael Greenstein

Mir S Seyed-Bolorforosh

Darwin Philip Adams

Benjamin M Herrick

David M Prater

Henry Yoshida

Thomas R Shrout

Joseph Fielding

Douglas Harriott

Sei-Joo Jang

Apparatus and methods for controlling electrostrictive transducer sensitivity in a pulse-echo medical ultrasound system. Certain characteristics of each transducer element are tested after manufacture and recorded on a storage medium. The stored data is then used, along with certain model relations, for monitoring certain operational parameters of the transducer during use, and feedback compensation applied for maintaining the transducer sensitivity substantially constant. The parameters to be monitored may include the temperature, acoustic pressure, input power, and a figure of merit determined from the dielectric constant and coupling coefficient.

Methods for controlling sensitivity of electrostrictive transducers

An ultrasonic probe for coupling acoustic signals between the probe and a medium is provided. The ultrasonic probe has a piezoelectric element having a plurality of piezoelectric layers each having a different acoustic impedance. The piezoelectric layers are stacked in progressive order of acoustic impedance such that the layer with the acoustic impedance nearest to that of the medium is proximate the medium. At least one of said piezoelectric layers is made of piezoelectric composite material. The ultrasonic probe further has an electrode means for electrically coupling the piezoelectric layers to a voltage source for applying an oscillation voltage potential to each piezoelectric layer. The probe further has a control means for controlling the polarization of at least one of the piezoelectric layers.

Hybrid piezoelectric for ultrasonic probes

Apparatus and methods for controlling electrostrictive transducer sensitivity in a pulse-echo medical ultrasound system. Certain characteristics of each transducer element are tested after manufacture and recorded on a storage medium. The stored data is then used, along with certain model relations, for monitoring certain operational parameters of the transducer during use, and feedback compensation applied for maintaining the transducer sensitivity substantailly constant. The parameters to be monitored may include the temperature, acoustic pressure, input power, and a figure of merit determined from the dielectric constant and coupling coefficient.

Apparatus and methods for controlling sensitivity of transducers

A tunable ultrasonic probe includes a body of a first piezoelectric material acoustically coupled in series with a body of a second piezoelectric material. The second piezoelectric material has a Curie temperature that is substantially different than that of the first piezoelectric material. Preferably, the first piezoelectric material is a conventional piezoelectric ceramic, such as lead zirconate titanate, while the second piezoelectric material is a relaxor ferroelectric ceramic, such as lead magnesium niobate. At an operating temperature of the probe, the first piezoelectric material has a fixed polarization. In contrast, the second piezoelectric material has a polarization that is variable relative to the fixed polarization of the first piezoelectric material. A preferred novel arrangement of electrodes electrically couples the bodies in parallel with one another. An oscillating voltage for exciting the acoustic signals in the probe is coupled with the electrodes. The polarization of the second piezoelectric material is variably controlled by a bias voltage coupled with the electrodes. In a preferred embodiment, the bias voltage has a reversible electrical polarity for selecting one resonant frequency from a plurality of resonant frequencies of the probe. In another preferred embodiment, the bias voltage source has a variable voltage level for selecting at least one of a plurality of resonant frequencies of the probe.

Tunable acoustic resonator for clinical ultrasonic transducers

A transducer for transmitting and receiving ultrasonic energy at more than one frequency includes first and second electrostrictive layers mechanically coupled together such that ultrasonic vibrations in one layer are coupled into the other layer. The first electrostrictive layer is laminated between upper and middle electrical contact layers, and the second electrostrictive layer is laminated between middle and lower electrical contact layers. A bias voltage arrangement selectively produces within the first and second electrostrictive layers electric fields oriented in opposite directions or electric fields oriented in the same direction. When the electric fields are oriented in opposite directions, the transducer has a first resonance frequency. When the electric fields are oriented in the same direction, the transducer has a second resonance frequency. By selecting the number of electrostrictive layers in a transducer and by selecting the thicknesses of different layers, a transducer having two or more different desired resonance frequencies may be produced.

Ultrasonic transducer having two or more resonance frequencies

An ultrasonic electrostrictive transducer for transmitting and receiving ultrasonic energy and having an expanded operating temperature range, preferably about room temperature. The transducers may be made from PMN-PT solid solutions having select mole percentages of PT and being doped with La, whereby the operating temperature range about a given operating temperature may be effectively doubled.

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North Andover, MA, United States of America

Turuvekere R Gururaja